ObjectivesTo evaluate the acute effects of 11 and 60 parts per million (ppm) inhaled nitric oxide on the pulmonary vascular resistance and systemic oxygenation of children with severe lung disease, and to compare the outcome of prolonged therapy with approximate 10 and 40 ppm inhaled nitric oxide.DesignProspective, randomized study.SettingA 26-bed pediatric intensive care unit in a tertiary children's hospital.PatientsNineteen patients (median age 11 yrs, range 7 months to 16 yrs) with acute bilateral lung disease requiring a positive end-expiratory pressure (PEEP) of more than 6 cm H2O and an FIO2of more than 0.5 for more than 12 hrs were treated with inhaled nitric oxide. One patient was treated twice during the same hospitalization.InterventionsAcute hemodynamic and blood gas effects of 11 and 60 ppm inhaled nitric oxide were studied, while delivering these concentrations in random order for intervals of 20 to 30 mins. Each interval was preceded by an interval of 20 to 30 mins without nitric oxide. Patients were then randomized and treated for a prolonged period with approximate 10 or 40 ppm inhaled nitric oxide independent of their initial acute responses to 11 and 60 ppm. Nitric oxide was discontinued when ventilatory support was decreased to a PEEP of less than equals 6 cm H2O and an FIO2of less than equals 0.5.Measurements and Main ResultsInhaled nitric oxide selectively decreased pulmonary vascular resistance and improved systemic oxygenation. Acute hemodynamic and blood gas effects of 11 and 60 ppm nitric oxide were similar. Systemic oxygenation improved to a greater extent in patients with radiographic evidence of residual aerated lung regions than in patients with diffuse bilateral lung disease. Maximum methemoglobin concentrations were greater in patients treated for a prolonged period with 40 ppm nitric oxide. The mortality and duration of therapy were similar for patients treated with 10 and 40 ppm inhaled nitric oxide.ConclusionsPulmonary vascular resistance and systemic oxygenation are acutely improved to a similar extent by 11 and 60 ppm inhaled nitric oxide, and concentrations in excess of 10 ppm are probably not needed for prolonged therapy of children with severe lung disease.(Crit Care Med 1996; 24:215-221)